Irreversible hydraulic pressure power actuator



March 3l, 1953 l.. E. BALDWIN l-:TAL 2,633,102

IRREvERsIBLE HYDRAULIC PRESSURE PowER AcTuAToR Filed Dec. 18, 195o i a sheets-sheet 1 v R R NR s l q n N ww R R. wf :111| R. @uw R m m m IR R www@ w Mb R. bw ,lNhf R n E Wr W Q A NN. u ILIIIIRIJRI .R NW QQ] R R R fm1 T E R mw MN Sv L0.

March 31, 1953 l.. E. BALDWIN Erm. 2,633,102

' V IRREVERSIBLE HYDRAULIC PRESSURE POWER AC'JUA'JORY Filed Dec. 18, 1950 5 Sheets-Sheei 2 la! ,137 l 39 .102 99 '100 J7! 170 v "o f.. a? -L3y202 *26 -62.

27 2 .f2.9 fw .13.1

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7 404 j?? 31 A J7! V 5 sheets-sheet 3 March 31, 1953 L. E. BALDWIN ErAL IRREvERsIBLE HYDRAULIC PRESSURE RowER Ac'TUAToR Filed Dec. 18. 195o JNVENToR l EE EI BALom//v BY Cre/z. M. Hen/vra learn ys cannot be forced to move in a direction opposite to that in which it is desired to move it, even when the reactive or resistive force greatly exceeds that exerted by the pilot, or even that exerted by the pilot and supplementary power system.'

Another object of the invention is to provide a system of the class described in which the follow-up is extremely close and accurate, thus resulting in positive and accurate positioning of the element actuated.

Still another object of the present invention is to substantially reduce the weight of the supplementary power equipment as compared to the weight of conventional supplementary equipment of the class described.

Yet another object of the invention is to provide a unitary structure which avoids the necessity of providing and installing miscellaneous fittings, fuses, valving units, and other costly items of equipment.

Still another object of the invention is to provide a system of the class described in which the ,movable elements can be moved, if desired, without supplemental power, and in which the forces Arequired to move the movable element during such times as the hydraulic pressure may be ofE" are relatively small.

A further object of the invention is to reduce the dead spot in the follow-up system to a .minimum whereby to eliminate undesirable and harmful vibration. y

An additional object of the invention is to provide a system having hydraulic pressure lines of materially decreased length whereby to increase hydraulic stability and reduce the effect of compression and decompression of air bubbles and cavitation in the fluid system, whereby to Vavoid the effects of deflection of the pressure .lines, and whereby to avoid the undesirable effects of kinetic pressure heads of the type above discussed.

The foregoing and additional objects and advantages of the invention will be apparent from the following detailed description of one embodiment thereof, such consideration being given l.also to the attached drawings, in which:

, Figure 1 is an elevational view of a hydraulic Yactuator for aircraft control surfaces, and a control unit therefor;

Figure 2 is an enlarged elevational, axial section of the left-end portion of the device shown .in Figure l, such section being taken in the plane .of Figure 1;

Figure 3 is an enlarged elevational section ,taken on the line 3-3 in Figure l;

Figure 4 is an elevational view of the device shown in Figure 1 as seen from the left end, porj tions being sectioned to disclose the internal construction;

Figure 5 is an elevational section taken on the `line 5-5 in Figure l;

Vline 8 3 in Figure 5;

Figure 9 is a perspective view of a check valve member forming a part of the construction of `Figure 1;

Figure 10 is a transverse elevational section taken on the line lil- I0 in Figure 2; and

Figures l1 through 14 are schematic diagrams showing the arrangement of vfluid passages inthe necting the control assembly and cylinder.

device illustrated in Figure 1, and showing said device in various successive operational positions.

The device illustrated in the drawings as disclosing a preferred embodiment of the present invention, is a unitary self-contained actuator for aircraft controls, such actuator being of the type in which, during normal operation, substantially all 0f the power required to move the control is supplied by the supplementary hydraulic system, the effort of the pilot being only that required to move a control valve. The system is so constructed and arranged, however, that in the event of a failure of hydraulic pressure, the movements and effort exerted by the pilot will be transmitted directly through the unit to the control surface being moved. Such taking over of the control operations by the pilot in the event of hydraulic pressure failure are fully automatic and require no special manipulation or other operation by the pilot.

The actuator shown in Figure 1 is intended to be included in a conventional thrust-tension control rod of the type in which reciprocal linear movements of the rod effect the desired movement of the movable control surface. Such control linkage being well known in the art, no detailed description thereof is necessary herein.

Referring to Figure l, it will be seen that the actuator comprises a double acting power actuating cylinder assembly 20, a -control assembly 2l, and a reciprocable connecting rod 2.2, con- At the left-hand end of the control assembly 2l is a short projecting rod 21, carrying a conventional fork or clevis 23 of the usual design adapted for connection to the manually moved control elements, and at the right-hand end of the power actuating cylinder 20 is a second fork 24 of similar design to that of the fork 23, the fork 24 being adapted for connection to the element to be moved.

As will be hereinafter described in more detail, a thrust rod 25 extends from the right-hand end of the cylinder 20, carries the fork 24, and is, in effect, an extension of the connecting rod 22. A body 3| of the control assembly 2l is irnmovably secured to the lefthand end of the connecting rod 22, and the control fork 23 is in turn connected tc the body 3| with a very small amount of lost motion between said elements, so that reciprocal axial movement of the fork 23 results in corresponding movement of the power fork 2li. Thus, the device is adapted to followup that is, as the power fork 24 is moved by hydraulic power, the control fork follows or moves with it.

The power actuating cylinder 20 is closed at its left-hand end by a pressure head 2E having formed therein a pair of diametrically opposed trunnions 28. The trunnions 28 are received in conventional fixed trunnion bearings (not shown) whereby to take the reactive thrust of the power actuating cylinder 20 during normal power on operation, as will hereinafter. be described.

The parts making up the power actuating cylinder 20 are best seen in Figures 2 and 3. Here Yit will be noted that the power actuating cylinder comprises an outer tube 32 having external threads 33 on the left-hand end thereof, `and an expanded or shoulder1 portion 34 on the righthand end. The shouldered portion 34 is internally threaded, as indicated at 35. The left-hand .end of the cylinder tube 32 is threaded into the head 26, and hermetically sealed therein by a con- .cross-no2? of theitu-be A32v and positioned "'in la fgroovein theL plug-39v is'iockecl inrplaceliby an internally splined spannernut 42 received in =thethreads -35.

Tv'Ihe iinterior `*of the power Aicyliimlerf tube 332 highly finished, as by lhoning, fand thas received therein-a slid-able piston 5` Iprovided-vvithr piston rings to seal athe `same- -against the i'I-i-terior surface @of the Stube 1i321. vrThe piston j'45 "is lfi1nmove/blyandhermeticallysecured to the connecting rod thrustrod 212-25l intermedia-teftheounc-f turevthereoi, whereby 1t-o forma cavity-1l?! "to the left of the-piston 45, and intermediate the vconnecting rod 22 and the tube 32, andlavsecondcav ityf48-to-'-the yright-of the piston ii5 iinter-mediate the thrust rod 25 and 4the -"tube132- Fluid perm` 49', "throughthe outer wall of 'the connecting Vrod 22, -and 15D, xthrough the outer wall o'f the ithrust rod 2'5,=serve to deliver fluid-into the cavities-l and 48, respectively, 4as ltvill hereinafter vbe described. Fluid may y-also fpass `out-:of 'the` cavities 4-1 -andif48, #through the `ports Quand .2511, respectively. I

'Thetconneo'ting rod1212'1is formed of fthreein-V teg-rally interconnected i concentricv itubes l353-, 5ft and i545, secured together :at their left-#hand fonds by an inner vannular spacer'ii-6 and an outer annular spacer 5l, and .at their right-handfends by anlinner spacerfS-E and 4an outer -annularfsp acer 5,9. The `tubes, 5B and 'ffarevsecuredito the spacersi', 51, 58 'and 5S -by copper brazing for similar means, `whereby lto *form -an integral -hermetrically Lsealed unit `having --an outer annular passageway i bilV between Ithefouter ltube 53 'and the intermediate vtube 54, -an intermediate'passageway 61 between the tubes 15d -and'55, `and "anfinner` passageway 62 `within vthe innermost concentric tube 55. The passageways 60,'61 fand=6l2` serve asthel sole means of fluid communication between thecontrol assembly 2i Land the-actuating f cylinder 412 0.

-Slidably received with-in 'the thrust lrod l25 and to"the-'rig'ht of 4the `piston *45 4a hydraulic accumulator /or' bungee "comprising 4a slidablejpiston -65`3having anfexternal O-ring'sealt, atoompression-spring B1, and aspring anchori'l secured in the right-hand end -oi the 4thrust rod25 by meansofinternal threads''il. The springanchor 68 is'lcckediinplace by the power Afork 24which is 4threaded tothe threads/69, and which in turn is held in place by an external flock nut 11. A lter .is'interposed between thefork ,2t andthe spring-anchor E8, the purpose rof `the lter *being to remove dirt from iairwhi'ch may be ldrawn into the `bungee air cavity Y'l2 through -an oriiice 13 inthe-'fork 2.4,'andspanner.holeshi in the'spring anchor'e.

Thus lfar it `will be 'seenthat the actuator assemblyZ is in essence a double acting fluid motor 4'and -can be operatedin 'the usual manner 'by connecting 'a 'four-way valve between lthe fluid ports J49-andf5il, 'and 'connecting the inletand returnjports of lsuch a four-'way valve to a source 'o'fi-ui'd' under pressure and to a'luid return. The vcontrolfasserrrbly "22|, about 'tob'e described, in- .cludes such a four-way valvebutiisifurther'modned-itcprevent` counterflow @of l'uidfbackeintozthef pressuretsource 'inf the-event the Y.reactive :'forcegof' the object' bieingzmoved. shouldiovercome theiforce exerted byithe motor. Further, itwsn'llibeascen,y

the Acontrolassemblyincludesfa pressure-operated; bypass- :valve :preserves `the lJirreversibility feature even when thef1ui`d1pressureitai1s and also :serves to ipermit#volumercompensating owfrom` one side :of ithe :piston :245i to rthe :other so as to fpermitiree manual operation ofithe. device.

inthef` eventoi` pressure lfailure.

"F.Iurning 4vnow J:to La V'discussion fof `fthe construction-of the-.control Iassembly M, Dit .will be fseen that/fithebod-y 3l -is closed iatfitsk ileft-hand rend' by a fplate LT1, andi its srighthand lend bylapla'te -l8,1the-iplates '111 and 11B 'ffbeinghermetically v.secured tto *the tendsnf' the body 35|' `'by .bolts-$19 threaded :into Jithe "-.l'atten :The rrghtehand :fend plate I8 is..tliametricallly.:sp1it, as` indicated 'Iby the reference character 80 'in iligure v5,.':softh'ftt the plate lf'lissadapted torernbracefthevfconnect ingrrod .2 '2:and; entera peripheralf-groove -81 there-,- in, :whereby to immovabl-yssecure 'the controlla-ssemblyzl to theconnectinglrodlzi.

"The .left-hand end :plate-11 is provided'lwithfsan extending 'rboss 182 having .Kan internal vpacking groove 83.therein, with packing-S84 insaidgroove. and a lubricating hole 85 through the'boss-if8`2liby which foil :or yother flubricant may- Iibe ysupplied :to the packing `8L', fito lubrcate the trod =.2I -'which f-.is slidable in the bossx 82,r as williherenafterbe 1del scribed.

V.The 'control assemblyHoody'1 3 I iis; *formed n:with eight longitudinal .bores, :as lican `be .seen best :in Figure '10. "These'bores comprise. fa main .bore 89: carrying `the ,main control Valve, an offset longitudinal bore 9U- carryingfa-.bypass;,valve, and six .radially .offset passagewaysi, r-92, `9 3, 94,195, and 96, each .of vwhichextencls iior `awpart:..only of thefull length ofthe .body 3l.

:The'body 3.1 .is ialso providedwith lateralfluid connections I9-"I .and 98, which Lare internally threaded to .receive :conventional tube ttings, 91 being `the inlet .or `pressure connection, Iand 98 being the outlet or return connection.

An extension 99 .of the outer tube .53 '.of` the connecting rod .'22 `extends throughout `the Amain bore..89, and contains within it a:f1ang ed liner sleeve IBG. 4'Iheextens'ion 93 provided'with :a number of .O-ring seals .surrounding A.the-.same to :seal it offagainst .the body 3.1, Vand-a number ofinternal 0-rings |02 to seal it .off against the sleeve LGB, pthe .latter 'being .held in place by the flange on the left-end thereof which is gclamped under .the lefthandend plate 11.

A number 4of 4radial `passageways communicate the internal bore of the sleeve l 0 0 with passageways in the body 3i. Such :radial passageways each comprise an undercut groove in the main bore '89, a Vrow of peripherally arrangedholes lin the ,tube extension `$19 underlying -such groove, an externalgroove in the liner sleeve |00 .underlying the last-.namedperipherallyarrangedholes, and a .plurality of peripherally arranged 4Vholes in the bottom of suchgroove .in the liner.

For convenience lin numbering the drawings, each of V,the composite radial passageways just `described will be identied by a single reference character, there being in all seven passageways identified in Figurebyth'e reference characters w3 'to H19, inclusive, reading `from left to right.

Theinterior of' the sleeve IDI] is `highly finished, as by honing 'and/or lapping, l'and has slidably receivedA therein `-a `valve spool 120. fThe spool HU isformed'with'amumber'ofanges the periphery lof'each of which is in fluid-tight sliding contactl with the interior of the bore through the liner |00. The spool flanges are identified by the reference characters |2| through |25, and as can be seen in Figures 2 and 6, provide between themselves a plurality of annular recesses |21 through |3I.` The permissible axial movement of the spool |20 within the bore of the liner |00 is such as to selectively intercommunicate various pairs of the radial passageways |03 through |09.

The spool |20 is formed with a stub shaft |34 projecting from the left-hand end thereof and received in a bore |33 in the right-hand end of the shaft 21. The spool |29 is connected for axial movement with the shaft 21 by means of a cross pin |35 extending through the shaft 21 and the stub |34. The shaft 21 is also connected with the slight amount of lost motion to the left-hand end plate 11 by means of a split ring |36 positioned in complemental grooves |31 and |38 formed in the end plate 11 and the rod 21, respectively. The groove |31, being somewhat wider than the split ring |36, a slight amount of lost motion as between the rod 21 and the control assembly 2| is permitted. Such lost motion, it will be realized, is that which eects and limits the movement of the spool |20 within the liner |00.

In the body 3|, in the offset bore 90 thereof, is positioned a fluid actuated bypass valve comprising a liner |4| having slidably mounted therein a movable spool |42, similar to the spool |20. External O-rings |43, positioned in grooves in theliner |4|, seal the same against the body 3|.

The bore within the liner |4| is closed at its left-hand end by a sealing plug |44, and at its right-hand end by` a similar plug |45. Plugs |44 and |45 are retained in place by the end plates 11 and 18, as can be seen in Figure 2.

Within the right-hand end plug |45 is a filter |46 of foraminous material, such as sintered metal, or the like, the purpose of which is to remove dirt from air that is drawn into the bore of the liner |4| by movement of the spool |42, as will hereinafter be described. A spring |41, positioned under the right-hand end plug |45 and anchored against the spool |42, serves to urge the same toward the left. An extension |48 on the right-hand end of the spool |42 serves several purposes, to wit, to hold the spool |42 during the finishing operation thereof, to center the spring |41, and to form a stop against the plug |45 to limit the rightward movement of the spool |42.

The liner |4| has a number of radial passageways formed therein similarly to the liner i00, the radial passageways in the liner |4| being identied by the reference characters through |55.

The valve spool |42 is formed with three flanges |51, |58 and |59, thus to form annular recesses similar in form and function to the recesses surrounding the main valve spool |20. As thus far described, it will be seen that the body 3| has ve fluid connections thereto, to wit, the pressure connection 91, the return connection 98, and the three concentric passageways in the connecting rod 22, identied by the reference characters 60, 6|, and 62. Movement of the two valve spools and |42 serves to interconnect and/or block various of the ve justmentioned fluid passageways in various combinations, as will hereinafter be described. In order to effect such intercommunication, certain other internal passageways in the body 3| are neces"-Y sary as follows.

Intercommunication of any one of the radial passageways leading from the main bore 89 with any of the offset partial length passageways 9| through 96 is effected by a so-called kidney cut, the shape and disposition of which can be seen in Figure 10, and is identified by the reference character |6|. By means of such kidney cuts, various of the radial passageways |03 through |09, and |5| through |55 are intercommunicated through one or another of the partial length longitudinal passageways 9| through 96.

Each of the partial length bores 9| through 96 is blind at one end and closed at the other end by a plug and O-ring |62| 63, as shown in Figure 7.

Certain of the passageways, e. g., 94 in Figure 7,-

are provided with check valves comprising a valve member |64 having lateral centering bosses |65 thereon, a conical forward surface |66, and a compression spring |61 positioned and adapted to urge the surface |66 against a seat |68 formed in the passageway 94.

In addition to the aforementioned radial passageways |03 through |09 which intercommunicate the interior of the valve liner |00 with various passageways in the body 3|, similar radial passageways |10, |1| and |12 serve to communicate the coaxial passageways 60 through 62, respectively, with passages in the body 3|.

Summing up the effective intercommunication of the various passageways just described, the result is as follows. The pressure connection 91 is communicated with radial bypass passageways I5| and |52 (the former by means of a small diagonal passage |13--see Figure 10). The radial passage |53 adjacent the bypass spool |42 is communicated by a kidney cut with the central radial passage |06 adjacent the main spool valve |20. The radial passage |54 adjacent the bypass valve is communicated with the radial passage |09 adjacent the main spool valve. The radial passage |55, adjacent the bypass valve, is connected to the return connection 98. The concentric passageways within the connecting rod 22, to wit, 60, 6| and 62, are connected to the radial passageways |10, |1| and |12, as has been described. Radial passageways |12 and |06 are intercommunicated by the partial length bore 9|. Radial passageways |03' and |09 are intercommunicated by the partial length passageway 96. Radial passageway |1| is also intercommunicated with radial passageway |04 by the partial length passage 95. Radial passageway |1| is also communicated with radial passageway |05 through partial length passageway 94, a `check valve |64 being interposed as shown in Figure 7. Similarly, as shown in Figure 8, radial passageway 1 0 is intercommunicated with radial passageways |08 and |01, through partial length passageways 92 and 93, respectively, the latter having a check valve |64 therein.

The system of fluid passageways produced by the foregoing structure is illustrated schematically in Figures ll through 14. For purposes of simplicity in the description, only a single reference character will be used to describe each branch passageway, although in fact such passageway may comprise several interconnected passageways, as just described. Also for purposes of simplicity, the various elements of the actuator assembly have been separated in the drawings, although it will be realized that they are closer together than shown in Figures 11 through 14, and are parts of a unitary structure rather tha separate elements as shown.

aces, 102

Qperatzon:y

'In' the condition shown in Figure 1'1, the-entire vsystem is filled' with fluid under substantially 'atmospheric pressure, and' thus the bungee 05 is in its position of minimum stress with the spring U61 completely expanded Also by reason ofthe bypassv'alvespring |41; the valve spool' |42 is held-in its lower-most position'in Figure I'l, thus `lo-prevent anyfescape offluid through the return ,fluid connection 98 or the pressure connection 97, and" interconnecting passageways |54 and |00 so as; toV permit free` circulation of fluid from and to the mainvalve spool |20, as will hereinafter be described.

' The conditionA in Figure 11v i's' that in which no fluidfisibeing delivered through theeinlet or pres fsureconnectionil'li Uponth'e application offluid pressure, the'condltion in' Figure 12 obtains. The bungee 65' is charged, andthe spring 61 compressedlwhereby to effecta predetermined sta-tic ypressurer oni'the entire system, even in the event theuid' delivery pressure should fail.

``Prfis'sure= applied atY the inlet connection 9i eile'cts'anupward force on the bypass'valvef'spool li4`2f, compressingth'e spring |421, and moving the valve ange v|58 upwardly so as to communicate the inletv connection 9'!Y with the passageway' |06 lwherebyf'to deliver Vfluid' under pressure to the 'chamber' adjacent the center-of the valve spool |2201 The'aforesaidupward motionk of the bypass Valve spool |42 also serves to intercommunicate the; passageway |09|`54 with the return duid connection 98"'whereby to permit huid to escape lfrom the upperend'oft'he' main valve chamber.

After' application of' pressure as just described, the operation of the actuator will depend on the l'position ofthe valve spool |20. In Figure 12, the spool. |20 is" shown in its intermediate or central position whereby' fluid is delivered from the central passageway |06 past the flanges |23 and |24 'through theH passageways 93 and 94 (notethe Ydisposition` of' the check valves |64)` to both the ,cylinder chambers 41 and 48 whereby the forces exerted onr the piston 45 are equaliz'ed and no motion of the thrust rod 25 results.'

It' shouldbe noted that when the system is in Vthe condition illustrated in Figure 12', a sudden reactive force on the thrust'ro'd 25' such'asl would beooccasioned by the buffting of the control surface connected thereto, will not result' in any "thrust'being transmitted throughthe system t'o -thevalve' spool" 20" and thence to the pilots manualcont'iol element. The foregoing is for'the r'ea- 'lsonthat*pressureonthe thrust rod 25 ywill `tend to "force fluid hackwardl'y'through either the pas'` fsagewayl'or the passagewayf l; It-willlbe-'noted "thati each'of thepassageways 60"and 6 I" connects 'witha pair of'parallel'branch passageway's (e. g.,

passageway lconnectsA with branch p'assageways 92and 93)", and' that one of saidbranchpassagereason'r off' the disposition ofthefch'ecli valves |64,

v such-rearwardlylmovingdluidcannot'-passthrough either* thepa'ssag'ew'ay 93 or 'the' passageway" 94'.

'outward thrust on thethrust rod 215;.` he applies appropriate., manual thrust: to th'e` spool |120 (through the control forleZif` and the rod-1251:):l thus: moving the? `valve spool' IBZ-.Bupwardlyf as slmwmimlliguref''. -Wheniinrthisrpositiomuid 'i's: .delivcree'l frfmrr.` the pressures connection 91 through the-1 passageway 06, the passageway 93, past the check valve |64, and through the passageway 6,0; into. the cylinder chamber 47,` thus urging the:piston..45. upwardly., In .similar fashion,` fluid is allowed` to-Y escape from the, cylinder chamber 48 through the passageway 5|, thepas.- sagewayf 95,l past theflange L22 which is now moved`- upwardly out of` the Way; through the pas? sageways |03, and |54', pastlthe bypass flange |59', and out` therreturn fluid. connection.` 98.`

Itwillbe obvious thattension` applied to the rod2J tomove thezvalvespool |20to. its lowermost positionL in Figures 11 through 14, will result in opera-tions exactly the reverseotthatjust describediin connection with` Figure 13. The; result.- of ,aupressure failure isA illustrated inzEgure 1.4;, Herefiawi'llfbe noted that therefmoyal of pressure,` fromthe. lower, end: of theby passwalve spool. |42l has permitted.; the. spring L41 to force` the samedownwardly against-its lowermost stop, closing offboththe-pressurefcon.- nection :and: the return connectionn 91, andv 98.,y respectively, andv intercommunicatingv the; passageways |,09fand |54.` Thusw-hile; no uidfpressune is yavailableto. assist the pilot in moving the thrust rod 25 onedirection:or-A the other,.the.1atter will beeprotected or. locked bythe operationcof the check valves Stagainstrearward, movement such",` for example; as that'fcaused by theafor'esaid buffeting, of the control surface; liork example, when thepilotv applies thrust to theY spool |20? in the manner previously described, the same is moved:V upwardly, thus 'placing' the system-inea condition: to allow' uid.- to: escape from.' thef cyl inderl chamber 48- in. thefmanner` previously de,-

scribed, whichl fluid` will circulate` through the passageway |54f adjacent the bypass valve and awayy therefrom through, the. passagewayl |016; to return through the passageway 93.1to-the opposite cylinderl chamber 4??. Shouldan-excessivereacf tive force be exerted?,onatheethrustrodMayhew ever, the previously described operation of the check valves |S4-will prevent backward or rearwardl movement of the rod 25,- even though the pilotlvmay be exerting only enough force tohold the valve spool` |2-0\in its upper position, as shown inFigure 14. v

Asanother example, suppose that the pressure having failed, the pilotdesired to move the-con trol surface to a` certain position andthenhold it there .against bueting forces in either direction. He would then move the spool |20.to..one or the other of its limiting positionsv and-force the-,lcontrol surface to the desired position, thereafterl relaxing his,l pressure.- to. return the. spool |20- to a neutralposition such as that sho-wn in-FigurelZ.

previously described, when'the spool |20 isin thisv position, the flanges |22 and |25close .01T thepassageways 92 and 95, thus trapping the fluid behind thecheck valves |64, `and preventing movementof the piston 45 in either direction.

The foregoing mode .of operation isi particularly useful in such craft asvhelicopters.wherein the reactive forces exerted by a control surface-.may often be cyclic, that. is, vary-ing between-a force which the pilot can overcomeand-a `force greater than thatw-hich the pilot'conveniently can exert.

Under suchconditions, it will stillbe possible for the pilotv to move the control surface into adesired-y position by continuingV to exert'` as much pressure as. possible* on theV lmovable I control.` element whereupon. each. time the reactive force dropsfbelnw tlla-texerted7 by the-pilot, thefsurface lwill.moveaesmalLamonnt inthedirection desired, but-whentthefreactiveforces momentarily exceed vaceaiot` 1l those exerted by the pilot, no countermovement will take place because of the aforesaid locking action effected by the check valves |64.

In some instances, it is desirable to incorporate a small amount of feel into the system, that is, to permit the reactive forces exerted by the control surfaces to be felt, in some degree, by the pilot. When such mode of operation is-desired, the check valves |64 are modified by drilling through the same to form a relatively small orice, such as indicated by the reference character '|15 in Figure 9. Thus, instead of -completely locking the piston 45 against movement, a small amount of fluid is allowed to leak out of one or the other of the cylinder chambers 41 and 48 through the appropriate check valve |64, so that Ythe thrust rod 25 continuously moves against a steady reactive force on the control surface. Such movement is then transmitted through the connecting rod 22, the valve body 3|, and the rod 21, back to the pilot.

It will be realized that, when modied as just described, the system also operates to damp out vibrational or buffeting reactive forces which act in rst one direction and then the other, since only a relatively slow reactive movement in one direction is permitted by the flow of uid through the relatively small orifice |15.

With even reasonable care in sealing 01T the system, it is possible to incorporate the same in a control assembly purely as an irreversible link, that is, with no pressurized fluid system connected. Furthermore, the irreversible feature disclosed herein can be used to considerable advantage in systems where substantially all of the force necessary to move the control surface is supplied by the pilot. In systems of the latter type, only a nominal amount of fluid pressure need be provided at the pressure inlet 91 for the purpose of restoring such uid as may leak from the system from time to time.

It will be seen that, due to the relatively short passageways between the control valve and the actuating cylinder, and due to the fact that such passageways are formed in rigid bodies, the responsive movement of the piston 45 as a result of control movement of the valve spool |20 will be extremely accurate since no iiuid will be consumed in expanding fluid lines or compressing air bubbles such as may be trapped in such lines. Furthermore, any air which may be trapped in the system will be compressed by the action of the bungee 65 so that its eiect will be kept to a minimum.

While the constructions shown and described herein are fully capable of achieving the objects and providing the advantages hereinbefore stated, it will be realized that such constructions are capable of considerable modification without departure from the spirit of the invention. For this reason, we do not mean to be limited to the forms shown and described, but rather to the scope of the appended claims,

We claim:

1. An irreversible lock for a movable, forcetransmitting member comprising: two immovable fluid chambers; movable wall means in said chambers to expand or contract the same; means connecting said wall means to said force-transmitting member for concurrent movement therewith such that one of said chambers is expanded when the other is contracted; a fluid passageway vintercommunicating said chambers whereby to permit fluid to iiow from one chamber to the other when said force-transmitting member is moved; and valve means interposed in said passageway, said valve means including at least one pair of parallel, branch passageways in one of which is a check valve formed with a restricted oriiice therethrough to permit relatively highly resisted counterflow of fluid therethrough, said check valve being disposed to restrict iiuid flow in a given direction, and a movable valving member disposed in the other of said branch passageways and mechanically connected to said force-transmitting member to close said second branch passageway when said member is moved in a direction to effect fluid flow in a direction opposite to said given direction.

2. Irreversible force-transmitting linkage comprising: a first movable member adapted for connection to an object to be moved; a second movable member adapted for connection to a source of actuating force and coupled by a lost ,motion connection to said rst member whereby forces in either of two selected directions may be transmitted from said source to said object through said members; a fluid-tight enclosure; a movable wall connected to said first member and disposed in said enclosure to hermetically divide the same into two chambers of mutually dependent volume; a passageway connected between said chambers to permit chamber volume compensating iiuid ow therebetween when said wall is moved; a valve body carried by one of said members and having a control passageway formed therein and interposed in said rst passageway, said control passageway having oppositely oriented check valves therein, and said body having a pair of bypasses formed therein, one around each of said check valves; and a valving member carried by the other of said rst two mem.- bers movable in said body between alternate positions to block one or the other of said bypasses.

3. The construction of claim 2 further characterized in that said check valves are each formed with restricted orifices therethrough to permit relatively highly resisted counterflow of fluid therethrough.

4. Irreversible power actuating linkage comprising in combination: a double acting hydraulic cylinder; a piston in said cylinder; a rod extending through said cylinder secured intermediate its ends to said piston and adapted by terminal attachment means for inclusion in a bidirectional force-transmitting system; conduit means including axially extending passageways in said rod, and a pair of liiuid ports in said rod to deliver fluid into portions of said cylinder on opposite sides of said piston; a four-way valve connected to said conduit means and adapted for connection to a source of fluid under pressure and a fluid return whereby said valve is operable to move said piston selectively in one direction or the other in said cylinder; a mechanical connection between said terminal attachment means and said valve, responsive to the direction of force transmitted through said rod to operate said valve concurrently with each change in direction of force transmitted by said rod; and hydraulic accumulator means in said rod including a spring-urged movable pressure wall and a separate axially extending passageway in said rod communicating said Haccumulator with said valve at a point therein adjacent the connection to said source.

5. Irreversible power actuating linkage comprising in combination: a double acting hydraulic cylinder; a piston in said cylinder; a rod decanos;

fluidtpressura-actuated-bypass valve normallydn'r` ter-posed: between: said inlet.: andi outlett and held said' normal position; by zsaid soumet pressure, Asaslchbyifiass-ivalve?beingzadapted' ytolmovetm block andinutlet" from said pressure-sourses and: returnLfrespectii/ely, and to; intercommunif-A cate said? inlets-and; outletvupon; thel pressure 'from source falling; vbelow arpredeterminedl min;- liinumzvalue;

67.' `Irreversiblet power-f 'actuatingf :linkage: com, prisingin. combination: a;V doublel acting;V hy- --ldragulief` cylinder a :pistons inf said:y cylinder; a, rod lextending', throughfsai d: cylin der Asecured Vinterino-- -diatefits endsftofsaidspistonland adapted by tenmina'l attachment: meansfor" inclusion:A in a4 bi'.- ,directionall forcef-transmitting` system; conduit .meanss-including, axially 4extending passageways mzfsaidfro'dtand aapair of.' fluid ports in said rod tofdeliven iiuid intofportionsA of', said. cylinder `on Yopplasitesides of. saidA4 piston;v afour-wayA Valve Iconnected?,to; saidl *cfmduitl means4V hav-ingi an inlet. .adapted-i forconnect-ion to affsource: of iiui'd Kunden pressure andaan outlet' adaptedy forV connect-ionfto, aiiuid return whereby to: move; said piston: selectively inf (one: direction;- on the: other in said cylinder; hydraulic:,aocumnlatonmeans vin said rodo inclu'dingj a spring-urged movable presslilefwallandiaiseparate axial passageway in said rod communicating said accumulator with said valve inlet;- and aafluidpressure actuated by- ,passsvalvef-normally interposed between said inlet and outlet and held in sai'dfnormal: position by said source. pressure, said bypass valve being adapted to move to blo'clr said inl'et and outlet from; said pressure source and return, respectively; andt to inter-'communicate 'said inletu and outlet-upon the'pressure from said source falling below a` predetermined minimum value:

'71. A yfluid `pi-'essure powerfactuator comprising .inrcombinations ao`loubler acting-fluid motor' having; extending foroe#transmittingA- member adaptedv for-fconneotionfto anfob'ject to be moved; af,"follettf-funrI-riemberl connectedto-said motorritor concurrentt'movementwithlsaid force --transmt- `ti-iig member; av control* member coupled lbyja lost motion connectionito-said follow-up member whereby, force may be applied through said fol.- lowmp member to said"forceftransmittingmeme per in addition 1:0 that appuedby saidmotor; a control valve body having an inlet adapted for connection to a source of iluid under pressure, an outlet adapted for connection to a fluid return, and supported on said follow-up member adjacent said lost-motion connection; a pair of passageways in said follow-up member to carry operating uid from said Valve to said motor and back to said valve; a valving member supported in said body for movement between alternate positions in which said motor is actuated in alternate directions, said valving member being secured to said control member whereby to be op- Verated tcxactuate said'. motorriniccordinaton with the forces applied thereto by saidcontrolfmenrber; andi means. to lock: said` motoriu against movement inra directicnoppositeeto thaturged by saidtcongtrolz` memben saidlocking: means; including; 'a

pair of.` branch passagewayst: forme'dj in ,said body and-"connectedat th'eir'juncturetto 'one' of :saidiirst passageways; the separate endszcf branch passageways being;v adjacent.- to,"l and :under .the control'l of; said valvi'ngl' member and; spaceidsc that one is cpenr when thenother; closed, `and one of said branch passageways having; a check valvetherein,

`8.\ A. duid! pressureizpower#actuator comprising in combination.: an: enclosed cylinder. .having .form-edf.thereon;trunnionsiwherebyttofsupportathesameiagainsiz axial mnvementg: :aL piston insa'id cylinder; .'a-'force,trans1nitting;'piston; .rodsecured .to saidpistomani extendinggthrougnrand beyond'anouterendaosaidcylinder; a-.follows-mp piston rosecuredftof. said piston-and extending through; and'beyondianinner'end of. saidfcylinder fon concurrent movement with saidspiston and force -transmittingzv rod;- ai-control member coupled, by ai. lost. motionv connection. tosaid fol,.- l'ow-up rod' whereby forcemay beapplied' tofsaid force-transmitting rodin addition to that applied by iiuid` pressure in' said, cylinder acting Von said,- pist'on;. a' control valve body having 'an inlet adapted for connection to.v ai. sourcel of. fluid yunder pressure;4 an outlet adapted for connection to afluidf return; and Supported onsaidifollorwflupf rod adjacent said; lost-motion connec tion' a. pair of axially extending passagewaysin said followup. rod to .carry operatingV fluidzfrom said valvetosaid cylinder;` a, pair of axially eX- ktending passageways in saidfollow-uprod', each connected by a port throughisaidrodtoa point in said cylinder on one crthe other sidefofzsaid piston whereby td carry operating-,fluid from 1 said valveto saidcylinder andi back to said. Valve; a

valvingmember supported int saidbody; for, movement between alternate positions in;V whichv said piston; isf actuated in. alternate rdirections .insaid cylinden. saidey valv-ing membery being@v mechanicallyiconnectedrtoesaid control member whereby to: befoperatedto' actuate said.- piston in coord-i1- Vnation Withforcesappliedr thereto by said lmember andfmeans to lockJ said i piston againstmoveyment inadirectionroppositeto that urged by said Ycontrol member, saidflocking meansvincluding'a lpairL ot branch passageways formed in saidjbody ,connected at Ytheir4 juncture `toyoneof'saidLV axially extending; passageways-i.. the..V separate ends .of 1said branch; passageways being; adjacent toi, and :nnderrthef controkcn'saids valvingmember. and Aso -spacedtthatz onefqis aliivews;open;wlsi'en.V ther-L other is closed;v oneofsaidl branch;passagewaysLhaving 9E The construction ofi claim 8 further'- cliari afcterizedr by having aJ secondA pair=of branchY pas- 'sageways' formed in: said bodfy and'- connected attheir iuncturerto the othenofl said"V axially-rex"- 't'ending passageways; the yseparateend's'` of said both closed 'whenever both of said check valve branches are open. 10. The construction of claim 9 further char acterized by having a fluid pressure actuated bypass valve disposed in said body and connected between said inlet and outlet, said bypass valve being responsive to pressure in said inlet whereby to block said inlet and outlet from said pressure source and return, respectively, and to intercommunicate said inlet and outlet upon the pressure at said inlet falling below a predetermined minimum value.

11. A fluid pressure power actuator comprising: a double acting fluid motor having two actuating chambers of mutually complemental volume; a control valve forsaid motor having .an inlet port, a discharge port, a pair of actuating ports, one communicated with each of .said chambers, and a valving member operatively associated with all of said ports and movable between two positions in either of which an alternate one of said chambers is communicated with said inlet port and at the same time the other chamber is communicated with said discharge port; a pressure passageway to deliver uid from an external source to said control valve; a return passageway to return fluid from said control valve to said source; and a fluid pressure actuated bypass valve interposed in said passageways and exposed to, and held by pressure at said pressure passageway in a rst position in which said inlet and discharge ports are blocked from each other and communicated respectively with said pressure and return passageways, said bypass valve being adapted upon a drop of pressure at said inlet passageway below a predetermined value, to move t a second position in which said passageways are blocked and said inlet and discharge ports are intercommunicated.

l2. A fluid pressure power actuator comprising: a double acting fluid motor having two actuating chambers of mutually complemental volume; a control valve for said motor having an inlet port, a discharge port, a pair of actuating ports, each communicated with one of said chambers, and each having a check valve therein oriented to prevent escape of fluid from said chamber through said actuating port; a pair of uid release ports, one communicated with each of said chambers, and a valving member operatively associated with said ports and movable between two positions in either of which the actuating port to an alternate one of said chambers is communicated with said inlet port, the release port from said chamber is blocked, and at the same time the actuatingvport to the other chamber is blocked and the release port therefrom communicated with said discharge port; a pressure passageway to deliver fluid from an eX- ternal source to said control valve; a return passageway to return iiuid from said control valve to said source; and a fluid pressure actuated bypass valve interposed in said passageway and exposed to, and held by pressure at said pressure passageway in a rst position in which said inlet and discharge ports are blocked from each other and communicated respectively with said pressure and return passageways, said bypass valve being adapted upon a drop of pressure at said inlet passageway below a predetermined value, to move to a second position in which said passageways are blocked and said inlet and discharge ports are intercommunicated.

13. A fluid pressure power actuator comprising in combination: a double acting iiuid motor having an extending force-transmitting member adapted for connection to an object to be moved; a control member coupled by a lost-motion connection to said force-transmitting member whereby force may be applied through the latter to said object in addition to that applied by said motor; a control valve having a body with an inlet to receive uid from a pressure source, an outlet to discharge fiuid for return to said source, a pair of passageways connected to conduct fluid to said motor and back to said valve, and a valving member supported in said body for movement therein between alternate positions in which said motor is actuated in alternate directions, one member of said body and valving member being supported on said force-transmitting member and the other on said control member whereby to actuate said motor in coordination with forces applied by said control member;v and means to lock said motor against movement in a direction opposite to that urged by said control member, said locking means including a pair of branch passageways formed in said body and connected at their juncture to one of said rst passageways, the separate ends of said passageways being adjacent to and under the control of said valving member and spaced so that one is open when the other is closed, and one of said branch passageways having a check valve therein.

LEE E. BALDWIN. CYRIL W. FRANKLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,258,337 Imblum Mar. 5, 1918 1,605,250 -McKenzie Nov. 2, 1926 2,012,861 Woolson Aug. 27, 1935 2,179,179 Fischel et al Nov. 7, 1939 2,293,555 Mercier Aug. 18, 1942 2,372,710 Chisholm, Jr Apr. 3, 1945 A2,474,630 Jamison June 28,-1949 2,482,249 Court Sept. 20, 1949 2,563,295 Westbury Aug. 7, 1951 2,566,273 vWestbury Aug. 28, 1951 FOREIGN PATENTS Number Country Date 487,909 Great Britain June 28, 1938 

